07.04.2019 – Week 9

Impact test

Benha University

Shoubra Faculty of Engineering

Mechanical Department

1st year Mech.

Prof. Farida Sayed Ahmed

Dr. Mahmoud Khedr

Outline

• Introduction.

• Impact testing.

• Izod impact test.

• Charpy impact test.

• Comparison.

• Failure modes.

• Solved example.

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07.04.2019 – Week 9

Introduction

Benha University

Shoubra Faculty of Engineering

Mechanical Department

1st year Mech.

Prof. Farida Sayed Ahmed

Dr. Mahmoud Khedr

Introduction

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fracture or to withstand impact.

Purpose of Impact Testing

• The purpose of impact testing is to measure an object's

ability to resist high-rate loading.

• It is usually thought of in terms of two objects striking

each other at high relative speeds.

• A part, or material's ability to resist impact often is

one of the determining factors in the service life of a

part, or in the suitability of a designated material for a

particular application.

• Impact resistance can be one of the most difficult

properties to quantify.

• The ability to quantify this property is a great advantage

in product liability and safety.

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07.04.2019 – Week 9

Impact testing

Benha University

Shoubra Faculty of Engineering

Mechanical Department

1st year Mech.

Prof. Farida Sayed Ahmed

Dr. Mahmoud Khedr

Impact test

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Impact test

The impact toughness of the specimen

is calculated by the formula:

• Q = U / A

Where

• Q-impact toughness,

• U – the work, required for breaking

the specimen

• U = M*g*H0 – M*g*H

• M: the pendulum mass,

• A: cross-section area of the specimen

at the notch.

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Standard Impact Tests

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07.04.2019 – Week 9

Izod test

Benha University

Shoubra Faculty of Engineering

Mechanical Department

1st year Mech.

Prof. Farida Sayed Ahmed

Dr. Mahmoud Khedr

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Izod Impact Test

Izod test

• Strikes at 167 Joules.

• Test specimen is held

vertically.

• Notch faces striker.

Izod Impact Test

Izod impact test

• The Izod impact test is the most common test in North

America. ASTM D256 and ISO 180.

• A pendulum swings on its track and strikes a notched,

cantilevered plastic sample.

• The energy lost (required to break the sample) as the

pendulum continues on its path is measured from the

distance of its follow through.

• Sample thickness is usually 1/8 in. (3.2 mm) but may

be up to 1/2 in. (12.7 mm).

• The result of the Izod test is reported in energy lost per

unit cross-sectional area at the notch (J/m²).

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Izod impact test

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Izod impact test

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.

07.04.2019 – Week 9

Charpy test

Benha University

Shoubra Faculty of Engineering

Mechanical Department

1st year Mech.

Prof. Farida Sayed Ahmed

Dr. Mahmoud Khedr

Charpy impact test

• Strikes form higher

position with 300 Joules.

• Test specimen is held

horizontally.

• Notch faces away from

striker.

Charpy impact test

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Charpy impact test

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Charpy impact test

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Comparison between Impact

Tests

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Comparison between Impact Tests

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07.04.2019 – Week 9

Watching the tests

Benha University

Shoubra Faculty of Engineering

Mechanical Department

1st year Mech.

Prof. Farida Sayed Ahmed

Dr. Mahmoud Khedr

1 Izod 2 Charpy

Failure modes

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07.04.2019 – Week 9

Strain energy

Benha University

Shoubra Faculty of Engineering

Mechanical Department

1st year Mech.

Prof. Farida Sayed Ahmed

Dr. Mahmoud Khedr

Strain Energy under Impact

Tension

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Internal strain energy

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External strain energy

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Elastic Impact tension

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Solved example

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